Process for creating fabrics with branched fibrils

ABSTRACT

The present process involves applying a plasticizer- or solvent-containing solution to a subject fabric, preferably under heated conditions, and then mechanically abrading the treated fabric. The process results in the rearrangement of the fabric structure, as a plurality of branched fibrils are created along the length of the yarn filaments. Thus, the molecular weight of the fabric&#39;s yarns and, therefore, the strength of the polymer chains are maintained. Fabrics made from this process, which exhibit a silk-like hand that results from the presence of multiple integral fibrils and branched fibrils, are also provided.

TECHNICAL FIELD

The present disclosure relates to a process for creating fine-scalemultiple fibrils and branched fibrils that are integrally connected tothe filaments from which they protrude. The process involvesmechanically abrading, preferably under heated conditions, a fabric towhich a plasticizer- or solvent-containing solution has been applied.The fabric containing such a fibrillated structure is also disclosed.

BACKGROUND

All patents described herein are hereby incorporated by reference.

There have been numerous attempts to modify synthetic fabrics(particularly polyester) to improve their hand and/or appearance.Conventionally, sanding or napping of the fabric has been used to softenthe hand and, in the case of continuous filament polyester fabric, todeluster the fabric. Sanding alone, however, typically results in largenumbers of broken yarn ends, in which the broken ends have substantiallythe same diameter as the originating yarns, thereby yielding a fabricwith a somewhat harsh hand and whitened and blurred surface.

Efforts to modify the surface of synthetic-containing fabric withspecialized finishing equipment have also been used with some degree ofsuccess. Various abrading mechanisms have been employed, includingabrasion with sandpaper, diamond grit, and the like, as described inU.S. Pat. No. 5,058,329 and U.S. Pat. No. 5,109,630, both to Love etal.; U.S. Pat. No. 5,815,896 to Dischler; and U.S. Pat. No. 5,819,816 toDischler. Further, subject fabrics have also been modified by treatmentwith high-pressure streams of air or water, as described in U.S. Pat.No. 4,918,795 to Dischler; U.S. Pat. No. 5,033,143 to Love, III; andU.S. Pat. No. 6,546,605 to Emery et al. The success of these efforts hasbeen largely dependent on the starting fabric and the desired results.However, these approaches failed to create the multiple and branchedfibrillated structure that is characteristic of the present process andproduct.

Others have attempted to create fibrillated, scale-like textilestructures through the use of chemical application combined withface-finishing techniques. U.S. Pat. Nos. 4,421,513 and 4,331,724 to Sudescribe a process for fibrillating polyester materials, which involveslowering the molecular weight of the polyester, treating it with a 100%concentrated swelling agent, and abrading the fabric. The result of thisprocess is a fabric that has scale-like fibrils projecting away from theconvex portion of the filament curvature (that is, the fibrils areproduced only on one side of the fabric at places along the filamentthat are exposed to abrasion). The fabric is also weakened because ofthe process used to reduce the molecular weight of the polyester. Thesereferences do not contemplate a dual-sided treatment of the fabric or amethod to enhance fibrillation to create multiple fibrils and fibrilswith multiple splitting.

An apparatus and process are described in U.S. Pat. Nos. 5,058,329 and5,109,630 to Love et al. to implement the art described in the Supatents. The process abrades fabric against a roll covered with roundedtungsten-carbide particles, after saturating the fabric with 100%methylene chloride at room temperature. The teachings of Love et al.fail to disclose a fabric having multiple fibrils and branched fibrilsthat are integrally connected to the filaments from which they protrude.

Yet another method of modifying fabrics is described in U.S. Pat. No.4,259,393 to Marco. Marco teaches treating a fabric containingtexturized polyester filaments with an alkaline solution in a jet-dyeingmachine in order to chemically break a substantial number of thefilaments. When the fibers break, the broken ends split into multiplefilaments as a result of their exposure to the alkaline solution atpreferred temperatures of between 45° C. and 55° C. Marco suggests thatsmaller filaments should project from each broken end. Like the Su andLove et al. references discussed above, Marco does not present a methodfor creating the multiple fibrils or branched fibrils that arecharacteristic of the present product.

SUMMARY

The present process involves applying a plasticizer- orsolvent-containing solution to a subject fabric, preferably under heatedconditions, and then mechanically abrading the treated fabric. Theprocess results in the rearrangement of the fabric structure, as aplurality of branched fibrils are created along the length of the yarnfilaments. Thus, the molecular weight of the fabric's yarns and,therefore, the strength of the polymer chains are maintained.

Benefits of the present process and product include, in one preferredembodiment, the use of relatively inexpensive yarns made entirely ofsingle-component polymers (as opposed to the use of multi-componentfilaments that are commonly described as being easily splittable or“island-in-the-sea”-type filaments). Fabrics made from the presentprocess retain their surface sharpness or clarify, making it possible tocreate fibrillated fabrics with fine-gauge stylized appearances.Further, fabrics made from this process exhibit a silk-like hand thatresults from the presence of multiple integral fibrils and branchedfibrils. In fact, the process achieves a microdenier-like soft handwithout the limitations of using microdenier fibers, which include poorabrasion resistance, difficulty in and a relatively higher expense ofdyeing, and poor lightfastness.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow-chart of the process of making a fibrillated fabric;and

FIGS. 2 through 6 are photomicrographs of fibrillated fabrics of thepresent disclosure, taken with an AMRAY scanning electron microscope,Model 1845 FE (1991).

DETAILED DESCRIPTION

As used herein, “fiber” is defined as a unit of matter, either naturalor manufactured, that forms the basic element of fabrics and othertextile structures. A fiber is characterized by having a length at least100 times its diameter or width.

“Fibrillation” is defined as the act or process of forming fibrils, suchas by breaking up a fiber into the minute fibrous elements from whichthe main structure is formed.

“Fibril” is defined as a tiny, threadlike element of a natural orsynthetic fiber that is still integrally attached to its parent filamentat one or both ends. A “branched fibril” is a threadlike element of anatural or synthetic fiber that is split into multiple smaller elements,all of the smaller elements originating from and being integrallyattached to the parent filament.

Fibrillation results in a fabric with finer filaments, as a plurality offibrils is formed from a portion of the filaments that is moved awayfrom the main body of the filaments. Thus, fibrillation is not anadditive or subtractive process, but rather a fiber rearrangementprocess. The advantage of this approach is that the fabric's overallweight is essentially unchanged.

Turning now to the drawings, FIG. 1 provides a flowchart of thepreferred present process for creating integral, branched fibrils on asubject fabric. Step 10 is to provide a fabric for modification. Fabricscontemplated for use with the present process include woven fabrics,knit fabrics, nonwoven fabrics, braided fabrics, pile fabrics, scrims,composites, spacer fabrics, and other fabric constructions as may beconventionally processed through a sander.

The fabrics may be made of yarns containing fiber types such aspolyesters, polyamides, polypropylenes, olefins and polyolefins,polyurethanes, aramids (such as Kevlar), acrylics, modacrylics, blendsof any of these fibers with one or more other fibers, and blends of anyof these fiber types with natural fibers (such as cotton). The presenceof natural fibers will not inhibit the effects of the present process onthe synthetic components of the fabric and may enhance certaincharacteristics of the natural fibers (e.g., hand). Preferably, theyarns are continuous filament yarns, although the process may be appliedto spun yarns as well. Most preferably, the yarns are polyester.

Before being subjected to the present process, the fabric may be dyed;calendered; embossed; coated; sheared; screen patterned; digitallypatterned by hot air, water, lasers, or the like; combined into acomposite; or printed. In one embodiment as will be discussed herein,the fabric is in its greige state when processed.

Step 20 involves the application of a chemical agent (specifically, afiber-specific plasticizer- or solvent-containing solution) to thefabric. Suitable application techniques include dipping, spraying, foamcoating, and other methods that may be known to those of skill in theart. Preferably, the plasticizer or solvent is part of an aqueoussolution. Suitable amounts of plasticizing agent range from about 0.1%to about 100% of the weight of the solution and, preferably, are fromabout 0.1% to about 10% of the weight of the solution.

Alternatively, step 20 can be accomplished in a batch-dyeing process(including jet-dyeing, beck dyeing, and the like), in which the fabricis placed in a pressurized vessel and baths are exhausted onto thefabric. In this environment, the fabric is typically agitated in a ropeform. Calculations of the amount of necessary fiber-specific plasticizeror solvent would be based on the weight of the fabric, rather than theweight of the solution. Preferably, when using a jet-dye machine, theplasticizing agent or solvent should be present in an amount of betweenabout 0.1% to about 10% of the weight of the fabric.

Preferred plasticizers for polyester include phenolic compounds (such aso-phenylphenol, p-phenylphenol, and methyl cresotinate), chlorinatedaromatic compounds (such as o-dichlorobenzene and1,3,5-trichlorobenzene), aromatic hydrocarbons and ethers (such asbiphenyl, methylbiphenyl, diphenyl oxide, 1-methylnapthalene,2-methylnaphthalene), aromatic esters (such as methyl benzoate, butylbenzoate, benzyl benzoate, and ethyl hexyl benzoate), and phthalates(such as dimethyl phthalate, diethyl phthalate, diallyl phthalate, anddimethyl terephthalate). Of these plasticizers for use with polyesterfibers, ethyl hexyl benzoate is preferred at amounts from about 0.1% toabout 10% of the weight of the solution.

Alternatively, certain solvents in which the fiber type may be at leastslightly soluble may be used in place of the plasticizer. Examples ofsuch solvents for use with polyester include n-methyl-2-pyrrolidone,propylene glycol n-butyl ether, propylene glycol n-phenyl ether,dipropylene glycol methyl ether, di-basic esters, andimidazole-containing solvents.

Solvents useful for other fiber types are documented in Handbook ofPolymer-Liquid Interaction Parameters and Solubility Parameters by AllanF. M. Barton (published 1990). By way of example only and notlimitation, solvents suitable for use with polyamides includetrifluoroethanol, trichloroethanol, phenol, cresols, halogenated aceticacids, and sulfuric acid. Examples of solvents suitable for use withpolypropylenes include n-hexane, 1-propanol, 1-butanol,methylcyclohexane, and tetrachloromethane.

One advantage of the present approach, when using plasticizer-containingsolutions, is a decrease in the amount of chemical agent that is used tomodify the fabric (for example, as compared with solvent-based systems).A further benefit is that the plasticizer- and solvent-containingsolutions contemplated for use herein are relatively easy and safe touse in large-scale manufacturing. Yet another benefit of usingplasticizer-containing solutions is that it provides a vehicle for thefibrillation of the fabric's fibers without the destruction of thefibers (that is, the fabric's structure is rearranged withoutsignificant weight or strength loss).

Step 30 is the optional application of heat to the fabric to which theplasticizer-containing solution has been added. Step 30 can beaccomplished either simultaneously with the application of theplasticizer-containing solution or subsequent to the application of theplasticizer-containing solution. It has been found that having theplasticizer-treated fabric hot can accelerate and enhance thefibrillation process, but it is not required. To achieve maximumproductivity, temperatures at the site of abrasion in the range of 40°C. to 100° C. are preferred, depending on the fiber type andplasticizing agent being used.

Step 40 is the mechanical abrasion of the fabric. Preferably, the fabricis mechanically abraded on both sides, although one-sided abrasion isalso possible. The fabric can be abraded using techniques such asneedling; napping; napping with diamond-coated napping wire; gritlesssanding; patterned sanding against an embossed surface; shot-peening;sand-blasting; particle bombardment; ice-blasting; tumbling; brushing;impregnated brush rolls; ultrasonic agitation; stone-washing; sueding;engraved or patterned roll abrasion; constricting through a jet orifice;impacting against or with another material, such as the same or adifferent fabric, abrasive substrates, steel wool, diamond grit rolls,tungsten carbide rolls, etched or scarred rolls, or sandpaper rolls; andthe like. The preferred abrading technique is described in U.S. Pat. No.5,819,816 to Dischler, in which the fabric is abraded against aplurality of diamond-grit rolls, allowing fabric-abrading speeds of upto 200 yards per minute. The mechanical abrasion of a fabric treatedwith a fiber-specific plasticizer results in a fabric whose filamentscontain a plurality of integral, branched fibrils.

Steps 50 through 80 are optional steps. Step 50 involves washing thefabric to remove any remaining plasticizer. Step 60 involves dyeing thefabric to a desired shade. Step 60 may also occur before Step 20, forinstance, in cases where the fabric is dyed before being treated orwhere the fabric is made from pre-dyed yarns. Step 70 involves dryingthe fabric. Step 80 involves printing the fabric, if so desired. Step 80may also occur before Step 20, for instance, as with the dyeing step.

The following Examples are representative of the present process andproduct.

EXAMPLE 1

A sample of woven 100% polyester continuous filament fabric was placedin a tensioning device, which applied about 12 pounds of tension perlinear inch in the warp direction of the fabric. The tensioning deviceheld the fabric close to a surface heated to about 125° C. A chemicaltreatment of 100% 1-methyl-imidazole was applied to the fabric untilsaturated. Immediately thereafter, an orbital abrasion device (having apiece of the untreated fabric as an abrasive) was pressed against thesaturated fabric at a pressure of about 2 pounds per square inch,abrading the saturated fabric for a period of about 3 minutes. Thesample was then removed from the heated surface and rinsed. The fabricwas examined using a scanning electron microscope, as shown in FIG. 2.

FIG. 2 is a photomicrograph at a 125× level of magnification of aplain-woven continuous filament polyester fabric, which illustrates thefibrillation that is characteristic of the present product. Thephotomicrograph shows a plurality of abraded fibrils that extend fromand are integral to the originating filaments. The fibrils, which arerandomly oriented with respect to the filaments from which theyoriginated, are present in the warp and fill direction of the fabric.FIG. 2 also illustrates that the fibrils can possess a very high aspectratio.

EXAMPLE 2

A sample of woven 100% polyester continuous filament fabric was placedin a tensioning device, which applied about 12 pounds of tension perlinear inch in the warp direction of the fabric. The tensioning deviceheld the fabric close to a surface heated to about 125° C. A chemicaltreatment of 100% polyethylene glycol methyl ether (molecularweight=750) was applied to the fabric until saturated. Immediatelythereafter, an orbital abrasion device (having a piece of the untreatedfabric as an abrasive) was pressed against the saturated fabric at apressure of about 2 pounds per square inch, abrading the saturatedfabric for a period of about 3 minutes. The sample was then removed fromthe heated surface and rinsed. The fabric was examined using a scanningelectron microscope, as shown in FIG. 3.

FIG. 3 is a photomicrograph at a 500× level of magnification of aplain-woven continuous filament polyester fabric, which illustrates thefibrillation that is characteristic of the present product. Thephotomicrograph shows considerable branched fibrillation of a brokenfilament in the fabric and overall fibrillation of the unbrokenfilaments. The breaking of filaments is a potential side effect of thepresent process that is deleterious to the overall strength of thefabric, but which may further modify the fabric hand.

EXAMPLE 3

A sample of woven 100% polyester continuous filament fabric was immersedfor thirty minutes in an aqueous chemical solution, brought to a rollingboil, including methyl benzoate at 9.5% of the weight of the solutionand surfactants at 0.5% of the weight of the solution. The fabric wasthen placed in a tensioning device, which applied about 12 pounds oftension per linear inch in the warp direction of the fabric. Thetensioning device was positioned over and held the fabric close to aporous steam vessel where steam was allowed to percolate through thefabric to reach a temperature approaching about 100° C. Immediatelythereafter, an orbital abrasion device (having a piece of the untreatedfabric as an abrasive) was pressed against the saturated fabric at apressure of about 2 pounds per square inch, abrading the saturatedfabric for a period of about 3 minutes. The sample was then removed fromthe heated surface and rinsed. The fabric was examined using a scanningelectron microscope, as shown in FIG. 4.

FIG. 4 is a photomicrograph at a 500× level of magnification of a wovencontinuous filament polyester fabric, which illustrates the fibrillationthat is characteristic of the present product and which furtherillustrates the intended effect of high aspect ratio fibrils that extendfrom parent filaments that are unbroken.

EXAMPLE 4

An aqueous bath was created containing 3% vinylimidazole and 3% butylbenzoate-based plasticizer, both based on the weight of the solution. A2-inch wide sample of woven 100% solution dyed polyester fabric havingtexturized continuous filaments was subjected to a continuous dipthrough the aqueous bath and over a system of rolls. The fabric wasabraded by threading the fabric through the rolls such that the fabricrubbed against itself under tension and in opposing directions over atwo-inch long zone of abrasion. The aqueous bath was recirculated tomaintain a temperature of between 60° C. and 80° C. The pressure used totension the fabric was about 40 pounds per linear inch in the warpdirection. The fabric was subjected to 120 cycles of abrasion. Thefabric was examined using a scanning electron microscope, as shown inFIG. 5.

FIG. 5 is a photomicrograph at a 250× level of magnification of a wovencontinuous filament polyester fabric, which shows the presence offibrillation on texturized polyester fibers that resulted from theprocess described above.

EXAMPLE 5

An aqueous bath was created containing 0.5% ethyl hexyl benzoate-basedplasticizer, which was heated in a dip pan by a steam jacket to maintaina temperature of about 70° C. A sample of a jacquard woven 100%polyester continuous filament fabric having solution dyed yarns waspassed through the aqueous bath and subsequently squeezed through niprolls. The fabric was incidentally cooled before being subjected toabrasion by a plurality of diamond-grit rolls over which the fabric wasthreaded. The diamond-grit rolls were not heated, although the additionof heat to the abrasive rolls or the abrading environment may bepreferred in some embodiments. The fabric was taken up and rinsed. Thefabric was examined using a scanning electron microscope, as shown inFIG. 6.

FIG. 6 is a photomicrograph at a 150× level of magnification of a wovencontinuous filament polyester fabric, which provides further evidence ofbranched fibrillation.

Thus, from the Examples, it can be appreciated that fine-scale multipleand branched fibrillation structure results from the use of the presentprocess. Fabrics fibrillated according to this approach may be useful asautomotive fabrics, napery fabrics, apparel fabrics, substrate fabrics,and for other end-uses where a modified fabric surface is desired. Byway of example only and not limitation, the fabric can be fibrillated inits greige state, dyed, and then combined with another material to makea composite that is useful as automotive seat cushions.

1. A process for creating a fibrillated fabric, said fabric comprising aplurality of continuous filament yarns, said process comprising thesteps of: (a) providing a fabric; (b) applying a fiber-specific chemicalagent to said fabric, said fiber-specific chemical agent comprising aplasticizer or solvent-containing solution; and (c) abrading said fabricto which the fiber-specific chemical agent has been applied, such thatat least some of said continuous filament yarns of said fabric havefibers from which multiple integral fibrils and multiple branchedfibrils protrude, thereby imparting in said fabric a silk-like hand. 2.The process of claim 1 wherein said fabric is selected from the groupconsisting of woven fabrics, knit fabrics, nonwoven fabrics, braidedfabrics, pile fabrics, scrims, and composites containing at least one ofthese fabrics.
 3. The process of claim 2 wherein said fabric is a wovenfabric.
 4. The process of claim 2 wherein said fabric is a knit fabric.5. The process of claim 1 wherein said continuous filament yarns areselected from the group consisting of polyesters, polyamides,polypropylenes, olefins, polyolefins, polyurethanes, aramids, acrylics,modacrylics, blends of any of these fibers with one or more otherfibers, and blends of any of these fiber types with natural fibers. 6.The process of claim 5 wherein said yarns are polyester.
 7. The processof claim 6 wherein said fiber-specific chemical agent is a plasticizerselected from the group consisting of phenolic compounds, chlorinatedaromatic compounds, aromatic hydrocarbons and ethers, aromatic esters,and phthalates.
 8. The process of claim 7 wherein said plasticizer ispresent in an amount of between about 0.1% to about 10% of the weight ofan aqueous solution into which said fabric is immersed in step (b). 9.The process of claim 6 wherein said fiber-specific chemical agent is asolvent selected from the group consisting of n-methyl-2-pyrrolidone,propylene glycol n-butyl ether, propylene glycol n-phenyl ether,dipropylene glycol methyl ether, di-basic esters, andimidazole-containing solvents.
 10. The process of claim 1 wherein saidfabric to which the fiber-specific chemical agent has been applied isheated between step (b) and step (c).
 11. The process of claim 1 whereinsaid fabric to which the fiber-specific chemical agent has been appliedis heated simultaneous with step (c).
 12. The process of claim 10wherein said fabric is heated to temperatures of between 40° C. and 100°C.
 13. The process of claim 1 wherein said abrading is accomplished by atechnique selected from the group consisting of needling; napping;napping with diamond-coated napping wire; gritless sanding; patternedsanding against an embossed surface; shot-peening; sand-blasting;particle bombardment; ice-blasting; tumbling; brushing; impregnatedbrush rolls; ultrasonic agitation; stone-washing; sueding; engraved rollabrasion; patterned roll abrasion; constricting through a jet orifice;and impacting against or with another material, said other materialbeing selected from the group consisting of the same fabric, a differentfabric, abrasive substrates, steel wool, diamond grit rolls, tungstencarbide rolls, etched rolls, scarred rolls, and sandpaper rolls.
 14. Theprocess of claim 13 wherein said abrading is accomplished by impactingsaid fabric against or with another material.
 15. The process of claim 1wherein said fabric is dyed after step (c).
 16. The process of claim 1wherein said fabric is printed after step (c). 17-25. (canceled)